Usually you need to go to your vehicles inventory, into assigned vehicles, and set yourself as the vehicle pilot. Then you can go to your position screen and there should be an "enter" or "board" button. Using that, you'll be able to get onto your vehicle, and can travel with it using the Enter Cockpit link, and travel button, much like walking around.

On a completely separate note, next time you ask for assistance, you're probably going to need to wait at least 2 hours for a response. That's MINIMUM before posting again. 20 minutes is WAY too little time to be repeatedly posting looking for an answer. People are less likely to help if you are impatient or rude.

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"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."